1. Field of the Invention
The present invention relates to a method of measuring the stiffness of an in vitro cultured tissue for determining the transplant compatibility of the cultured tissue, a method of determining the transplant compatibility of the cultured tissue, a quality-control method for the cultured tissue, and a method of preparing a transplant-compatible cultured tissue.
2. Description of the Related Art
Regeneration medicine and tissue engineering, in which cells are seeded and cultured in vitro on a tissue regeneration scaffold (base material or support medium) and a tissue is regenerated to thereby reconstruct a human tissue, and the reconstructed cultured tissue is applied onto a living human body to thereby treat the living body have received attention in recent years. Such cultured tissue for transplantation must be examined for compatibility (suitability) for transplantation upon the application to the living body or must be examined for suitability for shipment upon shipment from a supplier.
As a possible candidate for methods for the determination of transplant compatibility, for the successive determination of the culture conditions or for the determination upon shipment (offering), a method of observing the structure of a cultured tissue is known, in which part of the cultured tissue is cut to thereby prepare tissue cross-sections, a produced matrix is stained with a stain, and the resulting chromatic figure is observed under a microscope.
However, it takes a long time to prepare tissue cross-sections for examination and such microscopic observation requires great effort from, and places a load on the examiner. Additionally, in order to obtain chromatic figures for each observation, this method requires a large quantity of test tissue pieces overall since part of the cultured tissue must be cut to prepare test tissue pieces, other cultured tissue (cultured tissue pieces of the same lot) must be cultured in the same conditions, etc.
Alternatively, an attempt has been made to verify the relationship between the amount of a produced matrix and the stiffness of the cultured tissue by a method of measuring the stiffness of the cultured tissue, in which the cultured tissue is processed with, for example, a cork borer and is subjected to a destruction test such as a compression test. Such a destruction test requires, however, a large quantity of tissue test specimens as in the observation of chromatic figures, since the destruction method requires the tissue test specimens of another cultured tissue of the same lot.
In addition, cell growth depends on the age or other conditions of a cell provider (cell donor) or on the nature of individual cells, and the degree of growth subtly varies from one cultured tissue to another, and therefore it is difficult to predict, for example, the time needed to become a culture tissue suitable for transplantation. For example, the time when the cultured tissue becomes compatible for transplantation cannot be significantly predicted. The difficulty in prediction of the culture inhibits precise culture control for bringing the cultured tissue into a desired condition. For these reasons, the quality of the cultured tissue upon provision cannot be significantly stabilized and a transplant-compatible cultured tissue cannot be reliably and easily prepared.